You do not both need to live there. FHA allows a non-occupying co-borrower as long as one of you occupies a unit as a primary residence. On a duplex, though, there is a down payment catch to know about. The catch: FHA limits non-occupying co-borrower transactions to 75% loan-to-value. Family members can usually still get maximum financing (up to 96.5%), but that family exception does not extend to two-to-four unit properties. So on a duplex where your parent co-signs without living there, plan on roughly 25% down. Confirm the current rules for your exact structure, because this detail surprises a lot of buyers. Two more things shape the numbers: - Every borrower's debts count. FHA qualifies on blended ratios, so your parent's own housing payment, mortgage or rent, stays in the debt-to-income math along with their other obligations. - Rental income helps. With an owner living in one unit, FHA commonly counts 75% of the market rent on the other unit toward qualifying income, with the 25% haircut covering vacancy and upkeep, subject to documentation requirements for your file. The way to see whether this pencils is to run both incomes, both housing payments, the projected rent, and the down payment together. That is exactly what we map out in the free Roadmap conversation, about 20 minutes where we run your real numbers, so you get your actual qualifying picture rather than a rule of thumb.